This invention relates to a contact structure having a large number of contactors in a vertical direction for establishing electrical connections with contact targets, and more particularly, to a contact structure and its assembly mechanism for assembling a plurality of contact structures to form a contactor assembly of desired size, shape and number of contactors.
In testing high density and high speed electrical devices such as semiconductor wafers, LSI and VLSI circuits, a high performance contact structure such as a probe card having a large number of contactors must be used. The present invention is mainly directed to a contact structure and assembly of plural contact structures to be used in testing LSI and VLSI chips, semiconductor wafers, burn-in of semiconductor wafers and die, testing and burn-in of packaged semiconductor devices, printed circuit boards and the like. However, the present invention is not limited to the test applications noted above but can be used for any applications involving electrical connections such as forming leads or terminal pins of IC chips, IC packages or other electronic circuits and devices. Thus, in the following, the present invention is described with respect to the semiconductor device testing only for the simplicity of explanation.
In the case where semiconductor devices to be tested are in the form of a semiconductor wafer, a semiconductor test system, such as an IC tester is usually connected to a substrate handler, such as an automatic wafer prober, to automatically test the semiconductor wafer. The semiconductor wafers to be tested are automatically provided to a test position of a test head of the semiconductor test system by the substrate handler.
On the test head, the semiconductor wafer to be tested is provided with test signals generated by the semiconductor test system. The resultant output signals from the semiconductor wafer under test (IC circuits formed on the semiconductor wafer) are transmitted to the semiconductor test system. In the semiconductor test system, the output signals are compared with expected data to determine whether the IC circuits on the semiconductor wafer function correctly.
The test head and the substrate handler are connected through an interface component which includes a probe card or contactor assembly. A probe card has a large number of probe contactors (such as cantilevers or needles) to contact with contact targets such as circuit terminals or contact pads in the IC circuit on the semiconductor wafer under test. The probe contactors contact the contact targets of the semiconductor wafer to apply test signals to the semiconductor wafer and receive the resultant output signals from the wafer.
An example of such a probe card has an epoxy ring on which a plurality of probe contactors called needles or cantilevers are mounted. Because of signal path length of the components used in the conventional probe contactors is in the range of 20-30 mm without impedance matching, high speed operation or frequency bandwidth of the probe card is limited to the order of 200-300 MHz. In the semiconductor test industry, it is considered that the frequency bandwidth of 1 GHz or higher will be necessary in the near future. Further, it is desired in the industry that a probe card is capable of handling a large number of semiconductor devices, especially memory devices, such as 32 or more, in a parallel fashion to increase test throughput.
The size of the contact target such as a semiconductor wafer is increasing to produce as many IC chips as possible by one production process. Typically, the silicon wafer of today is as large as twelve inches or more in diameter. To increase the test throughput, it is ideal to use a probe card having a size and number of contactors compatible with the semiconductor wafer under test so as to test the overall wafer by a single contact operation.
However, in the conventional technology, probe cards available in the market are substantially smaller than the size of the semiconductor wafer, requiring many steps of contact operations by shifting the semiconductor wafer relative to the probe card. Thus, there is a need of a contact structure with a new concept which can dramatically increase the frequency bandwidth as well as the size of contactor assembly and the number of contactors mounted on the contactor assembly.
Therefore, it is an object of the present invention to provide a contact structure having a large number of contactors for electrically communicating with contact targets with a high frequency bandwidth, high pin counts and high contact performance as well as high reliability.
It is another object of the present invention to provide a contact structure and its assembly mechanism for assembling a plurality of contact structures to form a contactor assembly of desired size with desired number of contactors mounted on the contactor assembly.
It is a further object of the present invention to provide a contact structure such as a probe card to establish electrical connection with leads or pads of semiconductor devices for testing the semiconductor devices with high frequency bandwidth.
In the present invention, a contact structure for establishing electrical connection with contact targets is formed of a large number of contactors produced on a planar surface of a silicon substrate by a semiconductor production process including photolithography technology. The contact structure of the present invention has a specific structure in the outer edges so as to fit with other contact structures, thereby forming a contactor assembly of desired sizes and number of contactors to test a large sized semiconductor device such as a semiconductor wafer. The contact structure can be advantageously used for testing (including burn-in) a semiconductor wafers, packaged LSIs or printed circuit boards, but also can be used in applications other than the testing, such as in forming any electrical connections between two or more components.
The contact structure of the present invention is a block of a large contact structure or a contactor assembly for establishing electrical connection with contact targets. The contact structure is formed of a contact substrate and a plurality of contactors in which each of the contactors has a curved portion for exerting spring force in a vertical direction. The contact substrate has engagement mechanism at outer edges thereof so as to connect other contact substrates at any desired edges to establish the contactor assembly with desired size, shape and number of contactors.
In one aspect, the contactor is comprised of a tip portion which is protruded in a vertical direction to form a contact point, a base portion which is inserted in a through hole provided on the contact substrate in such a way that an end of the contactor functions as a contact pad for electrical connection at a bottom surface of the contact substrate, and a spring portion having a curved or diagonal or other shape provided between the tip portion and the base portion which produces a spring force when the contactor is pressed against the contact target.
In another aspect, the contactor is comprised of a straight body having a tip portion which is sharpened to form a contact point, a base portion which is inserted in the through hole provided on the contact substrate, and a spring portion having a curved, diagonal, ring like or other shape provided on the base portion which produces a spring force when the contactor is pressed against the contact target. The spring portion and the base portion of the contactor are inserted in the through hole of the contact substrate so that at least the spring portion be projected from the bottom surface of the contact substrate to function as a contact point for electrical communication with an external component.
According to the present invention, the contact structure has a very high frequency bandwidth to meet the test requirements of the next generation semiconductor technology. Each contact structure or contact substrate has the engagement mechanism at the outer edges thereof for creating the contactor assembly of desired size and desired number of contactors. Further, because the contactors are assembled on the same substrate material as that of the device under test, it is possible to compensate positional errors caused by temperature changes. Further, it is possible to produce a large number of contactors in the horizontal direction on the silicon substrate by using relatively simple technique. Such contactors are removed from the substrate and mounted on the contact substrate to form the contact structure in the vertical direction. The contact structure of the present invention is advantageously applied in testing a semiconductor wafer, packaged LSI, multi-chip module and the like including burn-in testing, although it can be used in any applications involving electrical connection.